The quick answer is yes.
In terms of the PAYG and 1MSO packages which are available in the market giffgaff beats everyone except Voxi, which as you say comes with a significant caveat.
So, in terms of raw value, in the markets which giffgaff are competing with, giffgaff is the undisputed market leader for all packages £10 and above.
Below £10 they can be beaten, but they have a couple of tricks up their sleeve here to make comparisons more complicated.
First, they'll give you cash for posting here on the forums if you have an active SIM card which can make those sub £10 packages cheaper or free with relative ease. They might even give you some pocket money on top depending on your contributions, (volume and quality).
Second they have free in-network calls and texts for three months from the date of your last top-up, so if you have a lot of friends and family on giffgaff your calls to them are going to be completely free no matter how many you make, as long as you top up once every three calendar months, (calls subject to a redial after 59 minutes to avoid charges).
So, in terms of raw value, (what you get in allowances/cost to you), yes, giffgaff is competitive, more than that, they're actually the best, (unless you're a heavy data/social media user and under 30, in which case, go with Voxi).
However, in terms of comparisons with 12MSO deals and handset deals, especially those offered on and around Black Friday, don't even bother with giffgaff or any other PAYG or 1MSO provider because they're a long, long way behind, the more data you need the wider the gap becomes.
Whilst giffgaff can compete with SOME 12MSO packages, and even beat them, (for instance Vodafone Red Extra £20/20GB is beaten by giffgaff who offer an extra GB of data after your third goodybag purchase making it £20/21GB), they won't come close most of the time, nor will any other company offering similar terms to what giffgaff offer.
Beyond cost and allowances that really comes down to personal preference regarding what you need and want you want.
Have they lost their "hype"?
This happened a long time ago but it's not to do with value for money and more to do with the fact that they lost their label as a cheeky, exciting, young upstart in the mobile market and became "just another provider", which was always gonna happen as innovation slowed, demographics changed and the other companies caught up.
Right now the most innovative network is Vodafone surprisingly. Yes, that old, slow, lumbering, monolithic network, with their Voxi product. The way they're embracing AI bots and going all in on social media is by far the most impressive thing any mobile network is doing right now, and it's not just Voxi they're doing it on, it's their entire range.
Even as someone who hates social media and doesn't really use it I'm super impressed with Vodafone and what they're doing there. It makes forums like this and even live chat support systems feel ancient and tired by comparison.