I bought a used '65 Deluxe Reverb several years ago, and really liked it for its portability and power. I play mostly slide and I'm always looking for a particular sound for my 335. The DRRI was about as close to what I wanted as I had ever gotten. I had a speaker cabinet with a 15" speaker modeled on the JBL 130DF that I plugged a Bandmaster VM into -- a pretty good sound, but not quite there. One day I idly unplugged the DRRI combo speaker and attached the 15. That spoiled the 12" for me, and I pondered ordering a custom head-only cab or maybe a custom combo cab to accommodate the 15. Soon enough I read about the head version and I sold the Deluxe.
I bought one of the initial run of the head-only from Sweetwater. Naturally, as soon as it arrived I set it on the 15 cab and plugged it in (as an aside, I had ordered the 15 in blackface livery so the components match). The few issues I had with the combo disappeared: no more too-present top end, the bottom became rounder, and the midrange more present.
This isn't really a review of the speaker, though, and I should tell you why I bought the head. The reverb is typically great Fender spring pan, the tone sings, and it takes a minimal amount of tweaking to find a sweet spot. I typically play my 335 though it, but it also shines when I plug in my Carvin equipped with Seymour Duncan Jazzmaster Antiquity II pickups. It's hard to make this amp sound bad, and the size and power output are all I need. As it happens, I am currently playing electric bass more than guitar, and the guitarist in my combo uses one of my amps in the music room to minimize hauling gear back and forth. He plays finger style on one of two 335s (trapeze and stop tail) through this Deluxe/15 and he makes them sing.
The Deluxe Reverb head is a valuable addition to my collection, and if you like to swap out speaker boxes you'll love having this amp in this configuration.