Hi, I have a Spider Jam that I have been using now for a few months. I wrote a review on it in the gear review section of these forums.
http://www.guitartricks.com/forum/showthread.php?t=29726A few things I would add now that I have used it for a while is:
I am an oldschooler when it comes to tone. I LOVE LOVE the tube amp sound and clarity. The Spider Jam is ALL digital. Altho many of the effects and stuff sound fairly decent, i could not get a statisfactory vintage tube sound from it. No substitute for the real thing for me.
Secondly, there are massive amounts of options, settings, etc to fiddle with. You can spend hours dialing in the sound you want.. luckily, you can save your own settings. If you are a plug in and go kinda person, it can be a little frustrating.
Lastly, it has this setting called a gate. In my opinion it serves no good purpose ,except annoying me. When on, it cuts your tone off in the beggining and end. Insted of a nice DDDDIIIIIIIiiiiinnnnnngggggg, you get hIIIIIIIiiing///. It sounds so terrible IMO and have found no isntance it sounded good. For some reason it turns itself on every time i start up the amp, and i have to scroll thru menues to turn it off. I have disabled it in the "startup menue" but it still comes on, and does it every time I switch the preset tones.
Line6 customer Service is laughable. They do NOT answere your questions. Instead, you sign up for a "Help forum" and ask your question. Other forum members chime in with there ideas, helpful sometimes, but you never get a real answer from the horses mouth.
These are all my just my opinions. I am an oldschool player, i like to plug in, turn it up to 11 and just play. BUT the jam tracks, drum machine, tuner and stuff are all awesome for practing scales, licks, and speed building. I use it for practice in that respect, but when I play for pleasure, or jam with friends, I use my Vox AC4TV.
As always, try before you buy. It may fit your style perfectly!