On a rare occasion I've driven on the motorway in the rain. With the hood down the only problem seems to be that the rain comes over the screen, mists the inside, and drips on your thighs. Take a towel and something to wipe the inside of the screen, like a microfibre water magnet cloth. It also runs up the mirror plinths and bubbles around the sidescreen frame on the inside of the doors. I stopped that with some extra seals. If you wear glasses, they may also get misted, but so far that hasn't been a problem.
With the hood up, it's cosy, a bit stuffy even, but with the side window open there's no draught on my Roadster, so it's not unpleasant. The wipers are adequate. Unless it's heaving down, you're better off with the half tonneau on and the hood down I reckon. I went over to Buxton on friday of Mog MMx in the wet with the hood down and quite enjoyed it!!!
