"Is it worth having?" Hmmm. Depends on what I'm teaching or doing, I suppose. In my calculator collection box I have all the calculators I've used in the last 35 years, hp and non-hp. So far it holds the 11C, 12C, 15C, 16C, 20S, 21S, 22S, 28C, 28S, 48SX, 49G, 49Gplus, 32SII, 42S, 200LX (with Derive) and finally the 50g (I sound like an HP junkie). Of course, at work (teaching) I've had to use the TI 81, 82, 83, 84, 85, 86, 89, and 92. Top down, I'd have to say my favorites are:
1) 42S
2) 200LX (not a calculator, but it is with Derive installed.)
3) 48SX
4) 32SII
5) 15C
6) 11C (my first, and probably the last I'd get rid of)
For the last 5 years I've carried around the 200lx and 42S. However, this last week these two have been usurped by the 50g. I'm not really sure how long it'll last, but I think it's certainly "worth" it.
Also, it's the only calculator on the planet (that I know of) that can graph simultaneous surfaces and rotate them (fast) to get a better visual of their intersections; huge to 4th quarter calculus students, and myself.
The 50g may easily move to the top of the list if it's still the only one in my bag this time next year. (I still go back to the 42S for the "simplicity" of it once in awhile, though.) But as has been mentioned, the "cost" or replacement factor of the 50g makes it "worth it" to me.
Happy computing,
CHUCK