1. Continual Light: Yes, it is a Light spell with infinite duration, but it's also a Light spell with double the area of effect - a 60' diameter sphere of illumination as opposed to 30' for the non-permanent version.
The permanence of the spell is a concern for some, especially if the game goes beyond mere dungeon crawling. Why, for instance, would not every settlement, from village to city, be lit by lamps of Continual Light? It costs the caster essentially nothing, and it lasts forever. Simplest solution: house rule that a caster may only have one Continual Light active at a time; casting another immediately extinguishes the previous one.
The reverse, Continual Darkness, is as one might expect, identical to standard Darkness but with double the area of effect and permanent duration.
2. Detect Evil: This does exactly what the 1st level cleric spell of the same name does, but with half the range (60' instead of 120') and a third the duration (2 turns instead of 6.) In fairness, good-and-evil stuff does seem to be more up the cleric's alley than the magic-user's, but then why isn't the reverse true for Detect Magic?
3. ESP: Does anyone else find the name of this spell odd and/or awkwardly anachronistic? I'm not sure what would be a better name - clairsentience, maybe? Anyway...what we have here is your basic mind-reading magic. It lets the caster "hear" the thoughts of a creature within 60', even from behind up to 2 feet of stone. This takes a full turn, so you're not going to outflank an enemy in combat by reading its tactical thoughts or anything like that. What the caster "hears" is at the DM's discretion, but probably includes such information as the creature's general disposition and state of mind. The use of the verb "hear" describing how the magic-user accesses its thoughts seems to suggest that the thoughts are "heard" as the creature thinks them, perhaps narrated in the creature's own mental voice; thus, the caster doesn't have access to all the target's knowledge and memories, but only those actively being thought about. The caster is magically able to understand the thoughts, regardless of the creature's language (or, presumably, lack thereof in the case of animals and such.) No saving throw is allowed, and the target creature is not made aware of the mind-reading.
Obviously, ESP will tell you for certain whether there's a living creature behind that door in the dungeon (undead are immune, though, so beware!) It's a big time ace-in-the-hole during negotiations - you can learn what the other side wants, how best to bribe/befriend/appease them, whether they're being honest or misleading you, and what their true intentions are. Any party wishing to avoid trouble as often as possible (that's ALL the smart ones) should be ecstatic to have a magic-user with this spell in his repertoire.
One might wonder why this spell wouldn't be used in courts of law, at least in major cities and the strongholds of the nobility. The streets may not exactly be teeming with 3rd level magic-users, but they're not that rare, either - there are bound to be at least a few within a ten-mile radius of a heavily-populated area.
4. Invisibility: It's hard to be stealthier than when you're literally invisible, and as long as you refrain from attacking or casting further spells, you stay invisible forever. Sneaking and spying are the most obvious uses, but the fact that it can be cast on an object instead of a creature opens up all sorts of intriguing possibilities. Since objects generally don't attack or cast spells (except perhaps in the case of traps), the logical inference is that the invisibility is simply permanent until dispelled. The spell description offers nothing more on the subject, so questions such as how big an object may be affected are left to the DM's judgment. The chest with the most valuable treasure in the dungeon could be hidden in plain sight this way. A bridge over a chasm might be made invisible. With a broad enough interpretation of "object," perhaps the water in a pool could be made invisible so that it appears to be empty. And that merchant who cheated the party last time they bought equipment in town - he'll NEVER find that dead fish you hid in his shop.
NPC magic-users could easily cast Invisibility on their undead or construct minions; left undisturbed, those minions might sit inert for centuries, waiting for intruders.
Interestingly, Invisibility has a range of 240'. Off the top of my head, it seems like this makes it a great "rescue" spell if a front line fighter gets himself in trouble in combat - just zap him invisible from afar and he disappears right before the enemy's eyes.