I'll probably edit this later on once I'm able to try out more of their selections, but for first impressions, this was a pretty nice place for a delicious lunch.
Ordered the regular-sized chicken parm sandwich, with mushrooms. The sandwich started at 6.50, plus about 88 cents for mushrooms. In hindsight, I should have ordered the free onions. Spice level was 'hot'.
The place has a cute logo, nice clean interior, if not particularly spacious. The man behind the cash was extremely friendly and very helpful in answering my questions regarding menu options.
It should be noted that all italian sandwich shoppes will be compared to California Sandwiches(CS) - I can't help it, it's just gonna happen, this is going to happen, so live with it.
On the other hand, On-A-Bun measures up quite well, actually. I have to admit that the fried chicken fillets were thinner and smaller than the same sandwich I get at CS, but the sauce was flavourful. They've achieved a very good balance between the tomato/parm sauce with the spiciness of the peppers - the jalapenos' are blended instead of diced chunks. In terms of construction, it was very well done - the sandwich was well put together and not very sloppy, although a mess on your fingers is still to be had (why else would you eat these?!).
TLDR: So how does it stack up? There was thinner chicken, but good sauce and good balance between sloppy and firmness. The price was also slightly lower, so that's a bonus.
I'll be back!