I love this model and have a ton of them in service between several locations. Agreed - just wait for a deal, as they go on sale often between amazon, microcenter, etc. I would say the sine wave functionality is worth it for the small premium.
And honestly, when the internal batteries start to go bad, they're super easy to replace and you're back up and running again. I usually put in 9ah batteries instead of 8ah batts. If you really depend on whatever you have plugged in, you may want to proactively plan on replacing the batteries every several (3 maybe) years, otherwise wait until it starts beeping at you and then swap out the batts with new. I've had some last a very very long time before they need batteries replaced. Also, use a labeler or something to indicate when you put fresh batteries into service.
APC devices are also great and have been around forever. You can't really go wrong with either of those two brands I think at this point.
I would say buy bigger than you think you need too, and don't plug anything into the battery side that doesn't really need it.