I use them pretty exclusively for my jobs, prob fit about 20 a year. I find them good quality and straight forward to fit but that could be because I was an MFI Premier Installer before they went bump so most of the methods of fitting are the same.
Haggle hard if you have the account and they can do some great deals. don't believe the people that say they aren't a big player like Ikea, they sell hundreds of thousands of kitchens a year and have as much warranty as anyone else, just your contact is through whoever supplied it to you (ie fitter) rather than direct with Howdens.
Their worktop is far better in quality than B&Q, Ikea etc. and in most cases about the same price. the End panels, plinth, cornice etc is also a lot better quality.
I'd rather have unfinished natural wood to sort as I like, that way you can install it how you like with the finish you like.