Pros: Lightweight, incredibly bright, competatively priced. Long battery life, but without added bulk of an external battery pack above your neck. Versatile modes - spotlight, floodlight, blinkers, and red LED for your star chart or secret missions. The recent redesign to a single LED provides for longer battery life in economic mode, and more lumens!
Cons: Witnessed a complaint that the push-button switch (push once, twice, three times to cycle through lamp modes) is annoying, but I didn't find this to be an actual issue for me. Maybe i'm just used to Petzl lamps? Also, some have complained that purple is really lame. This is not true at all. It is a fact that purple is very cool. Petzl does offer the Tikka XP 2 in Graphite (Grey) if purple isn't really your thing though.
I've found that this little headlamp is absolutely superb. Lightweight, burly and bright. In the economic (least bright) setting, the Tikka XP 2 provides 160 hours of burn time. I found the economic setting to be plenty bright for just about everything - reading, pumping water, cooking, hiking at night. The full brightness setting I reserve for times when you really need it - rock climbing, alpine climbing, skiing, spot-lighting something in the distance. I'd go through one set of regular Energizer AAAs in periods of 3-4 months. Maybe longer actually. Anyways, quite a long time.
The Tikka XP 2 is light enough to still be an option for thru hikers and casual backpackers alike, but rugged, efficient and bright enough to be useful in the alpine. Battery life does suffer in the cold (under freezing), and I noticed this on Shasta, Bailey and Mt. Ashland on several occasions. However, this can be easily bypassed by switching regular AAAs for lithium batteries, and this is pretty much true for any headlamp on the market. If you're going Caving or heading on a big trip to the Karakorum, South America, Alaska, or some place where extra batts might be tougher to find, and the cold is more severe - go with Petzl's Myo XP (designed for extreme environments). For anything in the U.S., I feel that this little purple headlamp is perfect.
The Wide Angle diffuser lens flips up easily with one hand when you need a floodlight, and can be flipped back down at a moment's notice to gain the added distance of Petzl's impressive spotlight. I found that I was able to do this with mitts on, even. The small tab on the lens is easy to grab. I definitely noticed that the redesigned single white LED provides a significant increase in both battery life and illumination when compared to the original. I've used both the classic Tikka XP and Tikka Plus, and truly feel that Petzl is innovating, not simply donning new flair.
The Tikka XP 2 is priced lower than most expedition headlamps, but is a little bit more expensive than your entry level lamp - They retail for $54.95.
This is the one headlamp I use for just about everything. I haven't really experienced anything negative about it in the last year. Go Petzl!