The first album was pretty crunchy, 'Doom' sounds like a good way to describe it... The second one Gothic was much better. As BF pointed out they are the inventors of Gothic Metal though, followed closely by Anathema and My Brying Died who were part of the same movement (they started a short time after PL).
I don't think they 'whimped out'. They made 3 dark and grim doom-ish Gothic albums, the time had come to evolve and go on as a band. Icon and Draconian Times is some of the most amazing shit I've ever heard. Given, some of the songs on Draconian Times are somewhat softer, but that's far from a bad thing as it's their best album imo. Icon is still full of pounding, wailing, crazy doomy riffs. And that man's voice
One Second / Host was a drastic change with all the electronics and stuff, but again I thought it was original and I really liked it. No matter what sound they had, Adam's bass kept tying everything together and kept it 'Paradise Lost' at all times imo. Believe In Nothing is soft and often disliked, but it's not as bad as people are making it out to be. Symbol Of Life is an amazing blend of metal and subtle electronics, the self-titled album isn't my favourite but it's still far from bad.
The last 3 albums are all steps back towards the roots, though far more refined. Greg Mackintosh making some heavy shit with his second band Vallenfyre really helped.
I probably belong to the few people who like all the different stages they've been through as a band