There's always an impression that the lens front element is a delicate bloom and must be treated with care.

Now, treating anything with care is always a good thing, but a lens front element has been designed to face the world. It has special coatings to deal with most things. Careful cleaning using a blower and microfibre cloth deals with most of the stuff that gets on it.

I'll say it again, though I may be proving myself wrong. I'm not trying to be evangelical about not using filters, but aside from specific cases I don't see a need myself. If other folk see things differently, that's all well and good.

This thread isn't about coffee then?

I've got Hoya Pro1 digital filters on both of my L series lenses, I've shot test images, with and without, inside and outside, and can see no difference in image quality or flare (with hoods obviously) at 100% RAW. Some argue that putting a filter on a top end lens can only reduce the image quality slightly, but I've not seen any evidence of that in my experience (on both cropped and full frame sensors). It saved me when doing a day shoot at sea a few years ago, I could wash the filter, or throw it away, far cheaper than ruining a £800 lens ruined.

However I did have a cheap Hoya Circular Polariser on a smaller lens a few years ago, and the poorer image quality from that was easily noticeable, I think I only used it once.

If money was no object I'd use B+Ws, but I'd rather spend £120+ on something more productive. There is a vast gulf of quality different between cheaper filters though, and it's worth doing a with/without test to a proper target.

Lens cleaners - I recommend the fantastic Giotto's Rocket air blower and the Hama lens pen, plus a good quality microfibre cloth too.

It turns out the listed as in stock filter will take up to 3 weeks to arrive. Hmmm Website lying much?!

For my own piece of mind I'm going to (when I can get it) put a filter on the new Tamron 17-50 and keep the one on the Sigma 50. I'm not fussed about one on the cheap Tamron 70-300. I think though if I can find one cheap enough I'm going to get a CPL for the 17-50 and a new (better) one for the 70-300 as the green series Hoya is pants!

If anything, I think this thread has redefined my thoughts on the matter.
Should you use a filter on the front?
Perhaps.

I've just spent some of the afternoon cleaning, dusting and fitting filters to 5 video cameras, because I don't trust the kids not to do silly things with them.
However, am I going to be quite so nervous about using my lens indoors without one? Of course not. On the beach? Absolutely.

That's my thinking. The whole point of this exercise for me is to get ready for wedding in Italy. I feel a bit safer, even if I ought not to, if there's a filter on the front.