I like my etrex 20. Use it for all our backcountry hikes as its small and light enough for me! Will be using it on our 120 mile alaska range trek this summer.
Another vote for eTrex 20 (with the OnXMaps chip). I can get 3 full days of battery life out of it. It doesn't have the digital compass like the eTrex 30 but a little silva fills that void.
I have the Oregon 550 and there are a few things I dislike about this unit.
The camera is pretty much useless. I usually have my phone so the extra money isn't worth it. I got mine on clearance for cheaper than the regular model. If that's the case the weight difference is minimal.
The touch screen is not as user friendly as smart phones. It can be very frustrating to use.
The screen can be very difficult to read when direct sunlight is hitting it.
With all that said I do not regret buying this unit. It's battery life is OK and is pretty easy to use. My next one will most likely be a 64 series.
The new Oregon 600 series is leaps and bounds about the 450's and 550's.
The new screen is made from mineral glass and is 100% scratch and shatter proof. I can't find the video now but there is one floating around of some German dudes beating the piss out of one to no avail.
The new screen is also unaffected by direct sunlight and totally usable with light weight gloves. I use mine with my Sitka merino's all the time.
Beyond that, you can now "pinch zoom" the screen like a smart phone and the screen will also rotate from portrait to landscape.
I never make tracks with mine, only check my topo and mark waypoints. With lithiums and fairly heavy use I can get 3-4 weeks on the battery.
Used a colorado 400t last year with 24k map chip. Bought this on ebay for $80. My buddy also bought the same. I used cheap alkaline and he used lithium batteries. He would get multiple days out of his unit while I would get a day maybe a little more. Overall this was an awesome unit to use in a fairly small package. I was lucky I bought this for my old garmin 72's screen went out a week before I left for CO. Glad that didn't happen in the middle of nowhere!