What is your opinion of this product?
I am very impressed with this combo amp. Great tone and plenty of punch. I had a G-K MB115, and this Fender just blows it out of the water for power and low end. Eventually, the G-K blew up, so I turned it into a speaker-only cab with an Eminence Delta 15 LFA, and I've been using that with a 410 cab for a couple of years now. Adding that 15 to this Fender Rumble makes it just as stage-worthy as my bigger rig. My main goal in buying this amp was to avoid lugging that big 410 up and down my basement stairs. It's surprisingly loud! Plenty for rehearsal and enough for anywhere if you run through a PA. 350W alone, 500W with an 8ohm ext. cab (Fender blurb only says 500 - not quite true).
I would have knocked off half a star for the overdrive section, though. It starts off way too fuzzy, so I really don't think it'll be all that useful to me - but I have a Sansamp Bass Driver Deluxe for that anyway.
Overall, this is a solid amp, especially with an extension cabinet. And it's light, too!