The "problem" is that the domain name does not pass the "radio test". If you advertise it on TV or in print media, people should remember it correctly, although there may be a small percentage who won't. So it's a branding issue mainly. In terms of perception by end users, it also suggests that you fell back on whatever was available because star.one is already taken obviously. Unless the keyword 'one' is part of your brand, and is a useful addition.
If your business is effectively named Star One, the domain name makes sense. If your business is named Star Solutions or something else, star1 looks artificial. Then you should probably consider a longer domain, close as much as possible to your real name, to minimize the risk of confusion.
But star1 is already taken anyway, unless you are contemplating another domain extension. If you could also register starone, then you cover all bases and this would solve the dilemma.
My advice would be to get the best name you can, and maybe consider an acquisition if the perfect name for you is available for sale. Or just go for a longer domain name. A longer name can still be memorable. I prefer a longer name, than a short name that is a potential source of confusion.
- how you intend to advertise and promote your brand
- your target market (Israel ?) - if your focus is the Israeli market and your business name is going to be "star ehad" I guess star1 could be viable. Or you could use starehad.com or whatever TLD... if you think about it, you are going to use an ASCII domain name, so it would make sense to transliterate the whole name.
But I really think that a mix of letters and digits seldom works well. I can't think of any well-known, global brand, using such a name.