I'm glad to hear you're liking it now. I picked up a '59 Bassman LTD not long after you got yours and I wasn't in love with it at first either. Just sounded brittle and harsh on the high end. I replaced the preamp tubes with Tung-Sol RI's and then learned how to properly bias the amp. It was set WAAAAY cold. That turned out to be the key issue. Once I brought the bias up into the "moderate" range (I didn't go hot as to preserve tube life) it completely changed the tone! Brittle highs were gone and it suddenly sounded warm. I'm even tempted to leave the RI Jensens in there since the prospect of dropping $400+ for new speakers on an amp I can't turn up loud enough to appreciate isn't really the best use of my money right now.
I think I'm going to use the BM for my gig coming up in a few weeks. It's going to be a place where the guitars have to go unmiked, so I want the BM not for the volume, but rather that wide even spread that only 4 10's can deliver.