As is my custom, I've just ordered myself a sweet new bit of gear for Christmas.
It's a Markbass Traveller 151P, to go with my superb CMD102P combo. Nice and portable. I got a good deal as well, looking at UK prices elsewhere. I've paid £405, delivered (absolutemusic.co.uk £415, minus £10 for using Google checkout - cool).
I occasionally use a Hartke 115xl as an extension cab, but the dang thing is just too heavy. The sound of a 15 with the 102P is just great, though, and at 37lb for the Traveller compared to 63lb for the Hartke cab, I may be inclined to inflict this awesome combination on people at a few more gigs.
I toyed with the idea of a 151HR, but it's only 10lb lighter than the Hartke. If I was going to lug that around, there's no real advantage as weight is the issue here, not tone. I don't really know how a small and light 115 like the Traveller will compete with a hefty beast like the Hartke. Despite the stick some Hartke stuff gets on here, the 115xl is a really good unit (as is the equally heavy 2.5xl I was using with it before I got the Markbass combo).
But a 1x15 cab at 37lb plus a 2x10 combo at 44lb should make a super light rig for that speaker configuration, and as long as it's somewhere close to what I've been using I'll be very happy with it. I'll let you know how it turns out.