My understanding is that Plaid have a good chance at taking Ynys Mon and Ceredigion in addition to holding onto their 3 seats due to a handy surge in Plaid's favour. If UKIP are as popular as they seem to be in the Anglophone parts of the Welsh-speaking territories (e.g. Holyhead) then they'll split the Labour/Lib Dem/Tory vote, arguably letting Plaid in through the back door.
I put some very small bets on seats I think will go ways I don't want - East Renfrewshire, Berwickshire, Glasgow North East and Edinburgh South if I remember correctly. I've got bets on East Renfrewshire, GNE and Edinburgh South staying Labour while Berwickshire goes Tory from Lib Dem. The odds are still in the SNP's favour in some of these seats but I'm preparing for the worst. I put a bet on the SNP winning less than 50 seats too. If it all goes "badly" I should win around £25 that I can spend on a 1ltr bottle of Teacher's whisky and drink until I forget.
Of course, I've been reminding myself all day that if the SNP win 15 seats it'll be the best result they've ever had. If they win 25 it'll be an earthquake, if they win 35 it'll be incredible (the first time they've ever won a Scottish Westminster election), if they win 45+ it'll be astounding...
5 PC seats would be the beginnings of them really looking to follow the SNP, and allow for a much greater credibility in the eyes of the English speaking parts of Wales - especially if those 5 MP's can take on a role in a government via Lab/SNP/Green/PC coalition. I do fancy PC in Ynys Mon, my home seat of Arfon (though both are far too close to call thanks to a strong old school Labour candidate in Arfon, and Holyhead being a Labour post industrial stronghold, both competing well with highly popular PC candidates with the rural community on their side), Ceredigion (Marginal PC/LibDem "should" go to PC thanks to LibDem capitulation), Dwyfor (theoretically safe), and Carmarthen (also theoretically safe).
What I really want to see is PC making inroads in the south. Can they push into 3rd or 2nd place in safe Lab/Tory seats? Could PC take Llanelli? That would only take a few thousands votes to swing. If so, it could provide a useful platform to move forward from in the future. Traditional heartlands are all well and good, but if PC want to get real change for the better in Wales, they need support that offers a mandate for said change. If not, the age old problem of how to make PC appeal to all sectors of welsh society remain. In some ways the lack of a language divide makes this so much easier for SNP.